VCO gain tuning using voltage measurements and frequency iteration

• US 20060145767A1
• Filed: 12/30/2004
• Published: 07/06/2006
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Vaananen, Paavo
• Granted Patent: US 7,148,760 B2
• Time in Patent Office: Days
• US Class Current: 331/16
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03J 2200/29 Self-calibration of a receiver
• CPC Class Codes: H03J 2200/36 Circuit arrangements for, e.g. increasing the tuning range, linearizing the voltage-capacitance relationship, lowering noise, constant slope in different bands
• CPC Class Codes: H03J 7/023 Neutralization of the automatic frequency correction during a tuning change
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H03J 7/10 Modification of automatic frequency control sensitivity or linearising automatic frequency control operation
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

This invention describes a method for gain tuning of a voltage-controlled oscillator of a phase locked loop (PLL) of an electronic device using voltage measurements and a frequency iteration. The invention presents a method of minimizing integrated VCO gain variations. More specifically, the invention implementation is based on an analysis which includes changing the VCO frequency by iteration steps and optionally calculating said iteration steps and measuring a gain of said voltage controlled oscillator (VCO) at said frequencies changed by the iteration steps, wherein the analysis is based on a predetermined criterion. The present invention can be used in any radio architecture that requires limiting of the VCO gain variation and tuning its center frequency.

Claims

1. A method for gain tuning of a voltage controlled oscillator (VCO) of a phase locked loop (PLL), comprising the steps of:

providing a VCO output signal of said voltage controlled oscillator to a phase detector module of said phase locked loop (PLL), wherein a frequency of said VCO output signal is optionally divided by an adjustable number determined by a divider control signal thus generating a divided VCO output signal;

providing a reference frequency signal containing a stable reference frequency corresponding to a frequency of said VCO output signal or optionally corresponding to said frequency divided by said adjustable number to said phase detector module;

generating a PD error signal by a phase detector module in response to said VCO output signal or to said divided VCO output signal, further in response to said reference frequency signal and optionally in response to said divider control signal, wherein said PD error signal is a VCO tuning voltage signal or said VCO tuning voltage signal is generated by low-pass filtering of said PD error signal;

generating a calibration signal and said divider control signal by a calibration control module in response to said VCO tuning voltage signal according to a predetermined criterion; and

providing said VCO tuning voltage signal and said calibration signal to said voltage controlled oscillator for implementing said gain tuning of said VCO output signal of said voltage controlled oscillator (VCO) according to said predetermined criterion.

2. The method of claim 1, wherein said VCO tuning voltage signal and said calibration signal are generated by analyzing according to said predetermined criterion, said VCO output signal and optionally by analyzing, according to said predetermined criterion, a selected number of previous VCO output signals provided to said calibration control module at pre-selected past time periods, wherein said pre-selected number is an integer of at least a value of one.

3. The method of claim 2, wherein said analysis based on said predetermined criterion contains changing said frequency by iteration steps and optionally calculating said iteration steps, and measuring a gain of said voltage controlled oscillator (VCO) at said frequency changed by said iteration steps, and said analysis is optionally performed by said calibration control module.

4. The method of claim 1, wherein said low-pass filtering of said PD error signal is performed by a low-pass filter.

5. The method of claim 1, wherein said divided VCO output signal is generated by a divider in response to said VCO output signal and to said divider control signal, and a clock signal indicative of said divided frequency is generated by said divider.

6. The method of claim 5, wherein said VCO tuning voltage signal is an analog format and converted to a digital format by an ADC block using said clock signal before said VCO tuning voltage signal is provided to said calibration control module.

7. The method of claim 1, wherein said VCO tuning voltage signal is provided to a voltage controlled oscillator core of said voltage controlled oscillator and optionally said VCO tuning voltage signal is an analog signal.

8. The method of claim 1, wherein said calibration signal is provided to a VCO calibration block of said voltage controlled oscillator, wherein optionally said calibration signal is a digital signal and said VCO calibration block is a digitally controlled capacitor.

9. The method of claim 1, wherein said voltage controlled oscillator (VCO) is a part of an electronic communication device and used for transmitting or for receiving information in said electronic communication device.

10. The method of claim 9, wherein said electronic communication device is a transmitter or a receiver, or both said transmitter and said receiver, or a portable communication device, or a mobile electronic device or a mobile phone.

11. The method of claim 9, wherein a user of said electronic communication device programs said calibration control module through a user interface for entering said predetermined criterion.

12. The method of claim 1, wherein said phase detector module contains a phase detector and optionally a charge pump.

13. A computer program product comprising:

a computer readable storage structure embodying computer program code thereon for execution by a computer processor with said computer program code characterized in that it includes instructions for performing the steps of the method of claim 1 indicated as being performed by any component recited in claim 1.

14. An electronic device capable of gain tuning of a voltage controlled oscillator (VCO) of a phase locked loop (PLL), comprising:

a voltage controlled oscillator, responsive to a VCO tuning voltage signal and to a calibration signal, for providing a VCO output signal, wherein optionally a frequency of said VCO output signal is divided by an adjustable number determined by a divider control signal, thus generating a divided VCO output signal;

a reference frequency module, for providing a reference frequency signal containing a stable reference frequency corresponding to a frequency of said VCO output signal or optionally corresponding to said frequency divided by said adjustable number;

a phase detector module, responsive to said reference frequency signal, responsive to said VCO output signal or said divided VCO output signal and optionally responsive to a divider control signal, for providing a PD error signal, wherein said PD error signal is said VCO tuning voltage signal or said VCO tuning voltage signal is generated by low-pass filtering of said PD error signal; and

a calibration control module, responsive to said VCO tuning voltage signal, for providing said calibration signal and said divider control signal to said voltage controlled oscillator for implementing said gain tuning of said VCO output signal of said voltage controlled oscillator (VCO) according to said predetermined criterion.

15. The electronic device of claim 14, wherein said VCO tuning voltage signal and said calibration signal are generated by analyzing, according to said predetermined criterion, said VCO output signal and optionally by analyzing, according to said predetermined criterion, a selected number of previous VCO output signals provided to said calibration control module at pre-selected past time periods, wherein said pre-selected number is an integer of at least a value of one.

16. The electronic device of claim 15, wherein said analysis based on said predetermined criterion contains changing said frequency by iteration steps and optionally calculating said iteration steps, and measuring a gain of said voltage controlled oscillator (VCO) at said frequency changed by said iteration steps, and said analysis is optionally performed by said calibration control module.

17. The electronic device of claim 14, further comprising:

a low-pass filter, responsive to said PD error signal, for providing said VCO tuning voltage signal by performing said low-pass filtering.

18. The electronic device of claim 14, further comprising:

a divider, responsive to said VCO output signal and to said divider control signal, for providing said divided VCO output signal and a clock signal indicative of said divided frequency is generated by said divider.

19. The electronic device of claim 18, wherein said VCO tuning voltage signal is an analog format, and said electronic communication device further comprises:

an ADC block, for converting said VCO tuning voltage signal to a digital format using said clock signal before said VCO tuning voltage signal is provided to said calibration control module.

20. The electronic device of claim 14, wherein said voltage controlled oscillator comprises:

a voltage controlled oscillator core, responsive to said VCO tuning voltage signal and optionally said VCO tuning voltage signal is an analog signal; and

a VCO calibration block, responsive to said calibration signal and optionally said calibration signal is a digital signal and said VCO calibration block is a digitally controlled capacitor.

21. The electronic device of claim 14, wherein said voltage controlled oscillator (VCO) is used for transmitting or for receiving information in said electronic device.

22. The electronic device of claim 14, wherein a user of said electronic device programs said calibration control module through a user interface for entering said predetermined criterion.

23. The electronic device of claim 14, wherein said electronic device is a transmitter or a receiver, or both said transmitter and said receiver, or an electronic communication device, or a portable communication device, or a mobile electronic device or a mobile phone.

24. An integrated circuit capable of gain tuning of a voltage controlled oscillator (VCO) of a phase locked loop (PLL), comprising:

a voltage controlled oscillator, responsive to a VCO tuning voltage signal and to a calibration signal, for providing a VCO output signal, wherein optionally a frequency of said VCO output signal is divided by an adjustable number determined by a divider control signal, thus generating a divided VCO output signal;

a phase detector module, responsive to a reference frequency signal containing a stable reference frequency, responsive to said VCO output signal or said divided VCO output signal and optionally responsive to a divider control signal, for providing a PD error signal, wherein said PD error signal is said VCO tuning voltage signal or said VCO tuning voltage signal is generated by low-pass filtering of said PD error signal; and

a calibration control module, responsive to said VCO tuning voltage signal, for providing said calibration signal and said divider control signal to said voltage controlled oscillator for implementing said gain tuning of said VCO output signal of said voltage controlled oscillator (VCO) according to said predetermined criterion.

25. The integrated circuit of claim 24, wherein said VCO tuning voltage signal and said calibration signal are generated by analyzing according to said predetermined criterion said VCO output signal and optionally by analyzing according to said predetermined criterion a selected number of previous VCO output signals provided to said calibration control module at pre-selected past time periods, wherein said pre-selected number is an integer of at least a value of one.

26. The integrated circuit of claim 25, wherein said analysis based on said predetermined criterion contains changing said frequency by iteration steps and optionally calculating said iteration steps, and measuring a gain of said voltage controlled oscillator (VCO) at said frequency changed by said iteration steps, and said analysis is optionally performed by said calibration control module.

27. The integrated circuit of claim 24, further comprising:

a reference frequency module, for providing said reference frequency signal containing said stable reference frequency corresponding to a frequency of said VCO output signal or optionally corresponding to said frequency divided by said adjustable number.